Accuracy and Reliability of MRI Reports in Diagnosing the Symptomatic Knee in Patients Who Had Bilateral MRI

Background: Newly symptomatic chronic musculoskeletal illness is often misinterpreted as new pathology, particularly when symptoms are first noticed after an event. In this study, we were interested in the accuracy and reliability of identifying the symptomatic knee based on bilateral MRI reports. Methods: We selected a consecutive sample of 30 occupational injury claimants, presenting with unilateral knee symptoms who had bilateral MRI on the same date. A group of blinded musculoskeletal radiologists dictated diagnostic reports, and all members of the Science of Variation Group (SOVG) were asked to indicate the symptomatic side based on the blinded reports. We compared diagnostic accuracy in a multilevel mixed-effects logistic regression model, and calculated interobserver agreement using Fleiss’ kappa. Results: Seventy-six surgeons completed the survey. The sensitivity of diagnosing the symptomatic side was 63%, the specificity was 58%, the positive predictive value was 70%, and the negative predictive value was 51%. There was slight agreement among observers (kappa= 0.17). Case descriptions did not improve diagnostic accuracy (Odds Ratio: 1.04; 95% CI: 0.87 to 1.3; P=0.65). Conclusion: Identifying the more symptomatic knee in adults based on MRI is unreliable and has limited accuracy, with or without information about demographics and mechanism of injury. When there is a dispute concerning the extent of the injury to a knee in a litigious, medico-legal setting such as Workers’ Compensation, consideration should be given to obtaining a comparison MRI of the uninjured, asymptomatic extremity.